RWBY Story: "The Reaper Of Grims"

Clyde has just barely recovered from the loss of his friends when he is moved to Beacon, the prestigious school that trains huntsman/tresses. But why did his friends die? What killed them? And why does he always have nightmares about their deaths? Why on Remnant is he still alive instead of Paige? And why does he feel like something is following him, staying near him, waiting for the perfect moment to strike?